Accessing Virtual Domains Locally

I have recently bought a Cisco SA540 which apparently has a major bug and I cannot view my websites using my domain locally. I can only access ISPconfigs main control panel but since the same ip applies to all the domains I can't reach other websites.

What do I need to do in order to access the websites of my ISPconfig 3 webserver using the servers DMZ ip?

Example: Instead of mydomain.com to type the IP address of the server 172.16.1.100/theWebsiteIwantToAccess so I can view them in my browser.

My problem is that my webserver is set as DMZ on the router. When I try to modify my host file to point ISPconfigServerIP to mydomain.com and www.mydomain.com I still get the same result.

I can't figure out how to do it even after downloading ISPconfig manual to see what possible solutions I can utilise based on what is written.

The theory is very straight forward: To create ip-based websites, but since I run multiple domains on one server which only has 1 ip address whatever I try it redirects it my routers main config page.

Is there a way to modify apache to understand and translate the ip with some kind of port to each website I want to access locally? Like for example myserverip:8282 to go to mydomain.com and myserverip:8383 to mydomain2.com?

Do you use local or public IP addresses in the hosts file? Because if you use local IP addresses, your router should not be involved.
If you use public IP addresses, make sure that your router is configured to forward port 80 to the ISPConfig server. If this still doesn't work, it is possible that your router doesn't support loopbacks.